android 4.3 Bluetooth ble don't called onChara

Question

I want to perform read and write operation with bluetooth peripheral.I have write sample application in which after giving particular input it give me output but inside code onCharacteristicRead not get called after onCharacteristicWrite. Please help me out.

This is my code

    BluetoothGattCharacteristic WriteCharacteristic =null;
    BluetoothGattCharacteristic ReadCharacteristic =null;
    private BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {

        /* State Machine Tracking */
        private int mState = 0;

        private void reset() { mState = 0; }

        private void advance() { 
            mState++;
            }

        public void onReliableWriteCompleted(BluetoothGatt gatt, int status) {
            Log.e("onReliableWriteCompleted", "Called");
        };


        @Override
        public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            Log.d(TAG, "Connection State Change: "+status+" -> "+connectionState(newState));
            if (status == BluetoothGatt.GATT_SUCCESS && newState==BluetoothProfile.STATE_CONNECTED) {
                /*
                 * Once successfully connected, we must next discover all the services on the
                 * device before we can read and write their characteristics.
                 */
                gatt.discoverServices();
                //String servicename = gatt.getService(BATTERY_DATA_CHAR).toString();
                //System.out.println(servicename);
                mHandler.sendMessage(Message.obtain(null, MSG_PROGRESS, "Discovering Services..."));
            } else if (status == BluetoothGatt.GATT_SUCCESS && newState == BluetoothProfile.STATE_DISCONNECTED) {
                /*
                 * If at any point we disconnect, send a message to clear the weather values
                 * out of the UI
                 */
                connectedDevice = null;
                mHandler.sendEmptyMessage(MSG_CLEAR);
            } else if (status != BluetoothGatt.GATT_SUCCESS) {
                /*
                 * If there is a failure at any stage, simply disconnect
                 */
                gatt.disconnect();
                connectedDevice = null;
            }
        }
        @Override
        public void onServicesDiscovered(BluetoothGatt gatt, int status) {
            Log.d(TAG, "Services Discovered: "+status);
            mHandler.sendMessage(Message.obtain(null, MSG_PROGRESS, "Enabling Sensors..."));
            /*
             * With services discovered, we are going to reset our state machine and start
             * working through the sensors we need to enable
             */
            //reset();
            String test="";
            List<BluetoothGattService> strname = gatt.getServices();
            String servicename =DINSTANCE_SERVICE.toString();
            for(int count=0;count<strname.size();count++)
                {
                    if(servicename.equalsIgnoreCase(strname.get(count).getUuid().toString()))
                        {

                        ReadCharacteristic = gatt.getService(DINSTANCE_SERVICE).getCharacteristic(DISTAINCE_READ_DATA);
                        WriteCharacteristic = gatt.getService(DINSTANCE_SERVICE).getCharacteristic(DISTANCE_WRITE_DATA);
                            test="123";
                            //characteristic.getStringValue(18);
                            //byte bbb[] = characteristic.getValue();
//                          gatt.readCharacteristic(characteristic);
                            /*String strInput = "012072";
                            byte passvalues[] = strInput.getBytes();
                            WriteCharacteristic.setValue(passvalues);
                            gatt.writeCharacteristic(WriteCharacteristic);*/

                            WriteCharacteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);
                            //tChar.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);
                            WriteCharacteristic.setValue(012072, BluetoothGattCharacteristic.FORMAT_SINT32, 0);
                            gatt.writeCharacteristic(WriteCharacteristic);
                            break;

                        }

                }
            System.out.println(servicename);
        }

        public void onDescriptorRead(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status) 
        {
            Log.e("onDescriptorRead","Read method gets called.");
        };

        @Override
        public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
            //For each read, pass the data up to the UI thread to update the display
            byte bbb[] = characteristic.getValue();
            if (HUMIDITY_DATA_CHAR.equals(characteristic.getUuid())) {
                mHandler.sendMessage(Message.obtain(null, MSG_HUMIDITY, characteristic));
            }
            if (PRESSURE_DATA_CHAR.equals(characteristic.getUuid())) {
                mHandler.sendMessage(Message.obtain(null, MSG_PRESSURE, characteristic));
            }
            if (PRESSURE_CAL_CHAR.equals(characteristic.getUuid())) {
                mHandler.sendMessage(Message.obtain(null, MSG_PRESSURE_CAL, characteristic));
            }
            if(DISTAINCE_READ_DATA.equals(characteristic.getUuid()))
                {
                    mHandler.sendMessage(Message.obtain(null, MSG_BATTERY, characteristic));
                }
            if(BATTERY_READ_CHAR.equals(characteristic.getUuid()))
                {
                    mHandler.sendMessage(Message.obtain(null, MSG_BATTERY, characteristic));
                }

            //After reading the initial value, next we enable notifications
            //setNotifyNextSensor(gatt);
        }

        @Override
        public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) 
        {
            //After writing the enable flag, next we read the initial value
//            readNextSensor(gatt);
            try {
                if (status != BluetoothGatt.GATT_SUCCESS)
                    throw new AssertionError("Error on char write");
                super.onCharacteristicWrite(gatt, characteristic, status);
                if (characteristic.getUuid().equals(DISTANCE_WRITE_DATA)) {
                    BluetoothGattService syncService = gatt.getService(DINSTANCE_SERVICE);
                    BluetoothGattCharacteristic tChar = syncService.getCharacteristic(DISTANCE_WRITE_DATA);
                    ReadCharacteristic = syncService.getCharacteristic(DISTAINCE_READ_DATA);
                    if (tChar == null)throw new AssertionError("characteristic null when sync time!");
                    tChar.setValue(012072,BluetoothGattCharacteristic.FORMAT_SINT32, 0);
                    gatt.readCharacteristic(ReadCharacteristic);
//                  gatt.readDescriptor(null);
                }
            } catch (AssertionError e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
            /*
             * After notifications are enabled, all updates from the device on characteristic
             * value changes will be posted here.  Similar to read, we hand these up to the
             * UI thread to update the display.
             */
            if (HUMIDITY_DATA_CHAR.equals(characteristic.getUuid())) {
                mHandler.sendMessage(Message.obtain(null, MSG_HUMIDITY, characteristic));
            }
            if (PRESSURE_DATA_CHAR.equals(characteristic.getUuid())) {
                mHandler.sendMessage(Message.obtain(null, MSG_PRESSURE, characteristic));
            }
            if (PRESSURE_CAL_CHAR.equals(characteristic.getUuid())) {
                mHandler.sendMessage(Message.obtain(null, MSG_PRESSURE_CAL, characteristic));
            }
        }

        @Override
        public void onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status) {
            //Once notifications are enabled, we move to the next sensor and start over with enable
            String strInput = "012072";
            byte passvalues[] = strInput.getBytes();
            descriptor.setValue(passvalues);
            advance();
            Log.e("onDescriptorWrite", "called");
            //enableNextSensor(gatt);
        }

        @Override
        public void onReadRemoteRssi(BluetoothGatt gatt, int rssi, int status) 
        {
            Log.e("onReadRemoteRssi", "called");
            Log.d(TAG, "Remote RSSI: "+rssi);
        }

        private String connectionState(int status) {
            switch (status) {
                case BluetoothProfile.STATE_CONNECTED:
                    return "Connected";
                case BluetoothProfile.STATE_DISCONNECTED:
                    return "Disconnected";
                case BluetoothProfile.STATE_CONNECTING:
                    return "Connecting";
                case BluetoothProfile.STATE_DISCONNECTING:
                    return "Disconnecting";
                default:
                    return String.valueOf(status);
            }
        }
    };

Answer 1

Here you can set up (subscribe) to the charactersitic through either notification or indication by calling:

mBluetoothGatt.setCharacteristicNotification(characteristic, true)
mBluetoothGatt.readCharacteristic(characteristic);

from here